rtfm
Well-Known Member
Hi,
I bought a copy of ADS - the aircraft design software by www.oad.aero. They sell five variants of the package, with the same underlying algorithms, but with (depending on version - and pricetag) has fewer or more features enabled. I bought the "Light" version - one down from the "Homebuilder" version - which has the comparison module disabled, meaning that you can't compare your creation with similar designs in the ADS database for cost, features, time to build etc.
The software is not exactly straightforward. First, there are a number of modules. Design, Analysis, Airfoils, Engines... The Airfoils module is impossible to use, and no sane person has any idea of how it works. Period. The Engine module lists an amazing array of Lycomings, Continentals and Rotax, including (surprisingly) the BMW 1200 and some oyther engines popular in Europe. But nothing even close to my Valley Engineering Big Twin. But after poking around in the engine files (just a text file) it wasn't difficult to clone one, and substitute the relevant details from my engine - weight, HP, CG, RPM, power output at various RPMs etc. And then save it as VE Big Twin.
After a bit of thought, it became apparent that I should Design before Analyse... See, I'm not THAT dumb.
Problem is, there are three levels of Design. Level 1, Level 2 and (surprise, surprise) Level 3 Each goes into increasing detail. Don't be like me and dive right in at level 3. There are many details which can't be entered without going through the preceding levels. So, start at level 1.
At this level, the parameters are somewhat generic. For example, the positioning of the wing is in percentage of the overall aircraft length and so on. And there are MANY MANY data points you need to enter. You will find yourself returning constantly to your CAD and your spreadsheets to measure. And the strangest measurements are required. Some obvious, but some are just unexpected.
This level of design makes all sorts of assumptions for you - like engine HP, fuselage length, wing area and so on. For example, it wants to know the ratio of tail area over wing area, but doesn't want to know the actual area of either.
Anyway, after completing all the screens (and there are a lot of them) you are advised that all information has been provided and you can "Compute". The PC goes into a frenzied whirring and blowing as it does its computations. It takes a good few minutes. And if your high-level parameters are feasible, you are informed that the design has resolved itself, and you are presented with a very comprehensive printout of just about everything imaginable. There are many hundreds of calculated data points.
On to Design level 2
This level adds details like wing placement (high, mid, low), tail configurations (all the usual culprits), gear config, and so on. Just about every screen now allows you to enter actual data rather than accept the calculated guesses provided by ADS in Design 1. Another Compute when all categories have green ticks next to them. And another printout. Typically, however, you will be provided with a number of "Cautions" ranging from obvious erros (CG too far back when fully loaded, prop too fine, etc). So you return, fix these and Calculate again and again till the errors fall away.
On to Design 3
At this level, you have a very fine-grained control over the data points. Great detail over the Wing, for example. Incidence at root and tip, airfoil at root and tip (not all airfoils are provided, but there are a LOT of them. No Ribletts, so I selected NACA747A315 at the root, and 415 at the tip, no washout. Likewise similar control over the tail feathers, actual placement of the wing (the datum is the tip of the spinner - so I had to re-measure everything). The weights are all calculated - as are the moment arms - but you can adjust the actual weights by adding an adjustment factor (eg ADS calculated my empty fuselage at 61 lbs. I know that it will weigh 43lbs. So I added a conversion factor of 0.705 to bring the weight down to 43lbs - etc. Actual moment arms can be entered manually.
Another Calculate.
This time, the planes performance in all its flight modes (plus whatever Cautions the system produces) is displayed. An iterative process of making adjustments (in my case it was having to moce the gas tank forward to get the CG within limits, and adjusting the pitch of the prop to prevent over-revving in the cruise).
Finally, a fully comprehensive printout of everything you could hope for. It would definitely satisfy any inspector, but more importantly for me anyway, it was a vindication of my design work to this point. Apart from having to move the gas tank forward about a foot, I had the design pretty spot on.
Max speed S&L @ 3000ft, 160mph on 50hp. Stall at 44mph.
Pretty damned impressive software, and certainly worth the $200 (ish) I paid for it.
Regards,
Duncan
I bought a copy of ADS - the aircraft design software by www.oad.aero. They sell five variants of the package, with the same underlying algorithms, but with (depending on version - and pricetag) has fewer or more features enabled. I bought the "Light" version - one down from the "Homebuilder" version - which has the comparison module disabled, meaning that you can't compare your creation with similar designs in the ADS database for cost, features, time to build etc.
The software is not exactly straightforward. First, there are a number of modules. Design, Analysis, Airfoils, Engines... The Airfoils module is impossible to use, and no sane person has any idea of how it works. Period. The Engine module lists an amazing array of Lycomings, Continentals and Rotax, including (surprisingly) the BMW 1200 and some oyther engines popular in Europe. But nothing even close to my Valley Engineering Big Twin. But after poking around in the engine files (just a text file) it wasn't difficult to clone one, and substitute the relevant details from my engine - weight, HP, CG, RPM, power output at various RPMs etc. And then save it as VE Big Twin.
After a bit of thought, it became apparent that I should Design before Analyse... See, I'm not THAT dumb.
Problem is, there are three levels of Design. Level 1, Level 2 and (surprise, surprise) Level 3 Each goes into increasing detail. Don't be like me and dive right in at level 3. There are many details which can't be entered without going through the preceding levels. So, start at level 1.
At this level, the parameters are somewhat generic. For example, the positioning of the wing is in percentage of the overall aircraft length and so on. And there are MANY MANY data points you need to enter. You will find yourself returning constantly to your CAD and your spreadsheets to measure. And the strangest measurements are required. Some obvious, but some are just unexpected.
This level of design makes all sorts of assumptions for you - like engine HP, fuselage length, wing area and so on. For example, it wants to know the ratio of tail area over wing area, but doesn't want to know the actual area of either.
Anyway, after completing all the screens (and there are a lot of them) you are advised that all information has been provided and you can "Compute". The PC goes into a frenzied whirring and blowing as it does its computations. It takes a good few minutes. And if your high-level parameters are feasible, you are informed that the design has resolved itself, and you are presented with a very comprehensive printout of just about everything imaginable. There are many hundreds of calculated data points.
On to Design level 2
This level adds details like wing placement (high, mid, low), tail configurations (all the usual culprits), gear config, and so on. Just about every screen now allows you to enter actual data rather than accept the calculated guesses provided by ADS in Design 1. Another Compute when all categories have green ticks next to them. And another printout. Typically, however, you will be provided with a number of "Cautions" ranging from obvious erros (CG too far back when fully loaded, prop too fine, etc). So you return, fix these and Calculate again and again till the errors fall away.
On to Design 3
At this level, you have a very fine-grained control over the data points. Great detail over the Wing, for example. Incidence at root and tip, airfoil at root and tip (not all airfoils are provided, but there are a LOT of them. No Ribletts, so I selected NACA747A315 at the root, and 415 at the tip, no washout. Likewise similar control over the tail feathers, actual placement of the wing (the datum is the tip of the spinner - so I had to re-measure everything). The weights are all calculated - as are the moment arms - but you can adjust the actual weights by adding an adjustment factor (eg ADS calculated my empty fuselage at 61 lbs. I know that it will weigh 43lbs. So I added a conversion factor of 0.705 to bring the weight down to 43lbs - etc. Actual moment arms can be entered manually.
Another Calculate.
This time, the planes performance in all its flight modes (plus whatever Cautions the system produces) is displayed. An iterative process of making adjustments (in my case it was having to moce the gas tank forward to get the CG within limits, and adjusting the pitch of the prop to prevent over-revving in the cruise).
Finally, a fully comprehensive printout of everything you could hope for. It would definitely satisfy any inspector, but more importantly for me anyway, it was a vindication of my design work to this point. Apart from having to move the gas tank forward about a foot, I had the design pretty spot on.
Max speed S&L @ 3000ft, 160mph on 50hp. Stall at 44mph.
Pretty damned impressive software, and certainly worth the $200 (ish) I paid for it.
Regards,
Duncan
